Little is known about suicide in older Veterans, and suicide-related behaviors (i.e., ideation, plans, and attempts), which are strong risk factors for actual suicide and strong indicators of extreme emotional and mental distress. Recent surveillance data from the Department of Veterans Affairs Suicide Prevention Program suggests that older Veterans are most at risk of committing suicide and require great need of care. The 2012 Suicide Data Report from the VA Mental Health Services Suicide Prevention Program documented that nearly 70% of Veteran suicides are in older Veterans (i.e., 50 years or older), and in Veterans using Veterans Health Administration (VHA) services it is nearly 80%. Furthermore, recent research has shown that less than half of VHA patients who killed themselves had a psychiatric disorder diagnosis; suggesting that other potential risk factors may be salient, such as medical and comorbid conditions, which are particularly pervasive in aging adults. In addition, Veterans 50 years and older are the largest proportion (> 70%) of the Veteran population and elderly Veterans are the fastest growing subgroup, with those aged 65 years and older comprising about 40% of Veterans in 2010 and almost 50% of Veterans in 2020. Yet, surprisingly, in this rapidly aging population of older Veterans at high risk of suicide, little is known about suicide, and even less s known about suicidal behavior. The implementation of many of the prevention programs by the VA are influenced by studies of younger military personnel and Veterans returning from combat. This has occurred, in part, because the prevalence and predictors of suicide and suicide-related behaviors among older Veterans nationwide have not been well characterized; yet, older adults compose the majority of the VA population. To this end, the primary goal of our study is to determine the prevalence and key predictors of suicide-related behaviors and suicide in older Veterans using four national databases, the Suicide Prevention and Application Network (SPAN) database, the Veteran Suicide Archive data, the National Patient Care Database (NPCD), and the Centers for Medicare and Medicaid Services (CMS) database. The SPAN and the Veteran Suicide Archive data will provide information on Veterans who have experienced suicide-related behaviors and completed suicide, while the NPCD and CMS data provide inpatient and outpatient information on medical and psychiatric diagnoses. The project proposes to make innovative use of the combined data and examine a large, nationally-based cohort of Veterans aged 50 years and older. In a very cost-efficient approach, this project will be the first comprehensive longitudinal examination of the prevalence and predictors of suicide and suicide-related behaviors in older Veterans. Key predictors, including sociodemographic variables, psychiatric disorders, chronic medical conditions, and comorbidity associated with suicide and suicidal behaviors will be determined (Aim 1), as well as dynamic risk factors (Aim 2)-assessing differences of associations overall and by age, gender, and race/ethnicity (Aim 3), and assessing the most important predictors and combinations of risk factors (i.e., highest risk subgroups) associated with developing suicidal behavior and completing suicide over the long term in older Veterans (Aim 4). Information stemming from this project will be important for identifying those older Veterans most at risk of suicide and with great need of care-helping to define national priorities for suicide prevention over the long term for all Veterans.